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Name: Ethan
Status: student
Grade: 9-12
Location: VA
Country: USA
Date: Winter 2012-2013

If a meteor hit Earth, how big would it have to be in order to effect the world?

Dear Ethan,

Good question. The meteor that hit Russia ;last week was coming in at about 18.65 km/sec and blew up at an altitude of 23.3m above the ground. Size is still uncertain but I would guess that it under ten meters across. It is the same size approximately, or maybe considerably smaller, than the Tunguska meteor that hit in 1908. These objects are too small to cause global damage. An object ten times that size, perhaps 100 meters, would send a shock wave that would be heard around the world but damage would still be relatively local.

An object half a kilometer or larger would strike the Earth and release a dust cloud that could very well cover the planet. Something a kilometer or more in size, like perhaps one of the larger pieces of Comet Shoemaker-Levy 9 that hit Jupiter in 1994, would definitely do considerable damage across our planet, including setting off fires around the world followed by a years-long atmospheric cooling. Finally, a comet or asteroid 10 kilometers across would do so much damage that it could extinguish most life on this planet.

So the short answer is that an object half-a-kilometer to a kilometer in size is the threshold to causing global damage.

Sincerely David H. Levy

Hi Ethan,

Thanks for the question. There are two main factors which determine how much Earth is affected by a meteor strike. The first is the size or mass of the meteor. The second is the speed of the meteor. Very roughly, a meteor the size of a football field (100 yards) traveling at twice the speed of sound would affect the entire Earth.

I hope this helps. Please let me know if you have more questions. Thanks Jeff Grell

You have a difficult question to answer, for several reasons.

First: You would need to define “What do you mean by “hitting the Earth”? The trajectory of the meteor and that of the Earth would depend upon whether the two bodies were “head – on” or glancing. Obviously, you would need to know the mass of the meteor. More importantly, you need to define the term: “What is the effect?” How do you want to define having the “effect”?

Your question would need to have a lot of parameters defined.

Vince Calder

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